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Difficulty: MediumLayer 2 Security Features (Port Security, DHCP Snooping, DAI)

A network administrator configures switchport port security on a Cisco Catalyst switch access port using the command 'switchport port-security mac-address sticky'. An end device is connected to the port, and the switch dynamically learns its MAC address into the running configuration. The administrator verifies full network connectivity, but does not enter any additional CLI commands before the switch undergoes an unexpected reboot. Which outcome occurs regarding the port security bindings after the switch reboots?

  1. The dynamically learned sticky MAC address is lost, requiring the switch to relearn the address upon new traffic arrival.Answer
  2. B
    The sticky MAC address is automatically written to NVRAM upon learning and persists through the switch reboot.
  3. C
    The switch converts the sticky MAC address into a static MAC address permanently stored in startup-config during shutdown.
  4. D
    The switch interface defaults to an err-disabled state upon reboot because learned sticky addresses trigger a native VLAN mismatch.

Answer

The dynamically learned sticky MAC address is lost, requiring the switch to relearn the address upon new traffic arrival.
When port security is configured with sticky MAC address learning, the switch automatically converts dynamically learned MAC addresses into sticky secure MAC addresses and places them into the running configuration in volatile RAM. Because the running configuration was not saved to NVRAM prior to the switch reboot, all dynamically added sticky MAC entries are erased, requiring the switch to relearn host MAC addresses once traffic resumes.

Step-by-Step Solution

1
Analyze how sticky MAC addresses function in switch memory.
Sticky MAC addresses learned by port security are appended directly to the active running configuration stored in RAM.
The switch dynamic sticky learning feature acts as a shortcut to add static configuration lines into running-config without manual MAC typing.
2
Evaluate the effect of a switch reboot when running configuration has not been saved.
RAM contents are lost during a reboot, reverting the switch to the startup configuration stored in NVRAM.
Without executing 'copy running-config startup-config' or 'write memory', any dynamically learned sticky MAC entries are purged.

Key Concept

Port Security Sticky MAC Persistence
Estimated Time:1m 15s
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Topics

Layer 2 Security Features (Port Security, DHCP Snooping, DAI)

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